1. Field of the Invention
The present invention relates to a webbing winding device which permits a rotation of a spool in a pull-out direction with larger than or equal to a force limiter load at least one of a time when a vehicle rapidly decelerates or a time when the spool rapidly rotates in the pull-out direction.
2. Related Art
In a belt winding unit disclosed in Japanese Patent Application National Publication No. 2003-502204, a belt shaft (a spool) and a locking side unit (a locking mechanism) are connected to each other through a torsion bar. Further, when the rotation of the locking unit is inhibited by sensing the state of a vehicle or a belt stripe, the torsion bar is twisted, so that the rotation of the belt shaft in the pull-out direction with larger than or equal to the force limiter load is permitted.
Further, the belt winding unit is equipped with a driving device, and the piston straightly moves when the driving device is operated. Furthermore, the piston pushes a step portion of an operation ring when the piston straightly moves, so that the operation ring moves in the axial direction. Accordingly, a claw which meshes with a torque tube provided inside the belt shaft swings, so that the meshing between the claw and the torque tube is released. Thus, the load value of the force limiter load changes from a high load to a low load.
However, in the belt winding unit, after the piston straightly moves with the operation of the driving device, the piston may move in the direction opposite to the movement direction due to the reaction. In this case, there is a possibility that the re-meshing between the claw and the torque tube is occurred so the load value of the force limiter load which has been changed to the low load is changed to the high load.